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Homework Help: Total differential

  1. May 6, 2008 #1
    1. The problem statement, all variables and given/known data

    For:
    z(x,y)=(x^2)y-3y
    Find [tex]\Delta[/tex]z and dz when x=4, y=3, [tex]\Delta[/tex]x=-0.01, [tex]\Delta[/tex]y=0.02

    2. Relevant equations



    3. The attempt at a solution

    I got the partial derivatives:

    df/dx=2xy, and df/dy=x^2-3

    and solved dz=0.02

    However, I don't know how to find [tex]\Delta[/tex]z
     
  2. jcsd
  3. May 6, 2008 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Delta z is the true difference. z(3.99,3.02)-z(4,3).
     
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